M30B35 Swap FAQ

[ZenitramNaes]

Can anyone answer the question about the 3 wire to 4 wire 02 wiring question that was posted in the first post? I'm unsure on how to wire my non OEM 02 sensor to the connector.

Am I right in assuming the following?

Grey-Ground
Black-Signal
White-Heater
White-Heater

You cannot assume anything when it comes to wire colors in the O2 harness itself. The only way to know what wire goes where is knowing the pinout of the sensor in question, and comparing it to the pinouts of the injection schematics from a B35 car's ETM. Or just buy the correct O2 sensor and make it easy on yourself.

I'm pretty sure I got that info from a good source, can't remember now. I ended up just going and buying a replacement.

[muz]

This a great write up, so much knowledge shared its fantastic. Having said that though my head is spinning with information overload, too much for my old brain.

I have just purchased an e28 535i (m30b34) auto and the PO has cut a lot of the engine harness during the removal of the engine in preparation for a jap engine transplant.

I have the engine, transmission, tail shaft etc to put it back together.

So, my question to the group is do I either:

1) Find a replacement harness and leave it with motronic 1.0 and chip it
2) Upgrade to motronic 1.3 and leave it
3) Upgrade to motronic 1.3 and chip it

I'm not after HP but more torque and better driveability. Any opinion is appreciated.

[Heathcliffe]

Can anyone answer the question about the 3 wire to 4 wire 02 wiring question that was posted in the first post? I'm unsure on how to wire my non OEM 02 sensor to the connector.

Am I right in assuming the following?

Grey-Ground
Black-Signal
White-Heater
White-Heater

Here's a couple things that may help. I just put Motronic 1.3 in my E24 swap so i went from a 3 wire system- the original 1.0- to a 4 wire system. The Bosch O2 sensor I used had the wire config that you posted above so it was 4 wire plug and play. The Motronic 1.0 doesn't require the grey ground return wire to the ecu which the 1.3 does. That being said you might be able to either cap the grey wire or just ground it to something as the case of the O2 sensor is grounded in both 3 and 4 wire applications. Page 1360-8 of the 87 ETM shows the
Motronic 1.0 3 wire config and page 1360-6 of the 89 ETM shows the Motronic 1.3 4 wire config. Here's a link for wire color for various O2 sensor manufacturers http://www.google.com/imgres?imgurl=&im ... CAUQsCUoAQ . Or you could buy a 3 wire sensor

[BuzzBomb]

Can anyone answer the question about the 3 wire to 4 wire 02 wiring question that was posted in the first post? I'm unsure on how to wire my non OEM 02 sensor to the connector.

Am I right in assuming the following?

Grey-Ground
Black-Signal
White-Heater
White-Heater

Or you could buy a 4 wire sensor

Fixed, and that he did.

[DJM1986-5]

I'm adding the correct part number for the right side motor mount bracket when using a late model B35 block and the Koala Motor sports adapter bracket.... The bracket needed is pn 11811175592
it's used on 533s and still shows available new for about $22.

[captbly]

So does the oil pan hit even using that Kola Motorsports bracket?

[DJM1986-5]

The oil pan does not even come close. I believe it has more ground clearance than the B34 but I did not take measurements - just appears so. I used both Koala motorsport adapter plates with my old B34 bracket on the left and the 533 bracket on the right side - perfect fit plus plenty of room for the long-tube headers. I need to post a picture of this.

[DJM1986-5]

One more thing I discovered - from the 179 ecu wires #40 and #41 need to be tied together and attached to the AC "on" signal from the AC switch....

After studying the wiring diagram for the AC circuit I discovered that pin #4 of C103 (on the B34 side) carries a green and yellow wire that comes from the AC switch. Along with engine speed and fuel on pins #1 and #3, I attached wires 40 and 41 to pin #4, all using a spare C103 male plug I clipped from an old B34 wiring harness. (Make sure to get at least two or three inches of wire along with the male C103 plug so butt connections are easier.

[tig]

As an addendum to those using the e24 B35 harness, who also are more inclined to use this chart by color and not pin number, there are a few differences between the e34 harness wire colors and e24 harness.
#2 = BU/VI (same as e28)
#7 = large GN (same as e28)
#8 = small GN *This needs to be spliced into #7 above or you get no + to represent "key on" to the ECU, meaning no start.
#10 = BU/WT (same as e28)
And some of the unused wiring is different than the chart, but aren't necessary to note.
Since a lot of people are more visual and rely on colors in a schematic, it's good to know these differences.

I thought I had an E34 harness. I was stumped as to why #2 was BU/VI according to my multimeter and not GN/YL as the chart shows. Now I know I actually bought an E24 harness. Thanks!

[tig]

One more thing I discovered - from the 179 ecu wires #40 and #41 need to be tied together and attached to the AC "on" signal from the AC switch....

After studying the wiring diagram for the AC circuit I discovered that pin #4 of C103 (on the B34 side) carries a green and yellow wire that comes from the AC switch. Along with engine speed and fuel on pins #1 and #3, I attached wires 40 and 41 to pin #4, all using a spare C103 male plug I clipped from an old B34 wiring harness. (Make sure to get at least two or three inches of wire along with the male C103 plug so butt connections are easier.

Thanks. Good info; glad I saw it. Some more info to further clarify with pics:

Here's C103 under dash.


Here's C103 on a B34 harness.


Page 6411-0 of the ETM shows pin 4 of C103 as GN/YL "Not used".

I had a spare E28 harness and pulled the male C103 off of it. I then pulled the male of this, whatever it is, and broke the male part apart to extract the pin out from inside it.


I used that pin to add a pin to #4 on the C103:

[tig]

I've read and re-read this thread regarding the coolant temp sensor/coolant temp sender. I got totally confused and had to step back to make sure I really understood. Hopefully this will help others.

The B35 has two coolant temp thingies that are plugged into the thermostat housing.

Coolant Temp Sensor
This puppy feeds the ECU with info on the engine temp. It connects with two wires via a BLUE connector (at least on my E24 B35 harness). The wires that run to it are BR/RT and BR/OR. The BR/RT goes to pin 45 of the DME. BR/OR is ground.


Coolant Temp Sender
This goes to the instrument cluster and drives the temperature gauge. It connects with two wires via a BLACK connector. The wires that run to it are BR/VI and BR/GE (GE is yellow). On an E34 both wires go to the the cluster. It appears BR/GE is power and BR/VI is the sender.


The B34 has three thingies plugged into the thermostat housing: A Coolant Temp Sensor, Sender, and the Thermotime Swtich. The Thermotime Switch is not needed on the B35.

The B34 Sender has one wire (the B35 has two per above).


The E28 cluster has a BR/VI wire leading to it that feeds the temperature gauge. If you are using a B34 Sender, then the BR/VI wire from the harness (was going to pin 4 on the 20X connector) will go to the BR/WH wire at pin 4 of the C101.

This is super straight forward, so I'm not sure why others had temp gauges that didn't work. Maybe it's because they were using B35 Senders?

[tig]

I have a question about pin 14 of the 20X. BK/WH (SW/WS) wire that goes to the ECU "Speed Signal Input". I believe this is Pin 29 on the ECU. The E34 ETM shows the cluster as having a "Vehicle Speed Output" that goes to Pin 29 of the ECU.

In the wiring chart above, there's no E28 connection for this. Am I correct in my understanding that on an E34/E24 etc... this is an input INTO the ECU from the speedometer and that ECU does something with this...and that this is not really needed (hence no angst over not connecting it on an E28)?

Mostly just curious.

[tig]

I'm really struggling to figure out how to wire in my harness. My problem is that I am un-willing to just blindly splice things together when either the colors or pin #s in the previous posts are ambiguous. I need to understand what goes where.

My 20X connector/harness does not seem to map up to all of the mappings above and I've taken to my multimeter to try to figure out what's going on.

My B35 harness, has these connectors near the ECU plug. I figured out what they are all for.



From Left to Right:

White 4 pin - X79 - This is for the ABS pump; not necessary on E28s, but you'll want to use two of the leads...
R (12V)
BK/GN (From Starter; I think this goes hot when "Starting")
BK/GR (ECU - Pin 40 - AC Low Pressure Cutoff)
BK/BL (ECU - Pin 41 - A/C On input - ETM says "Aux Fan")

You'll want to tie both the BK/GR and BK/BL to the #4 pin on the C103.

Black 4 pin - X1552 - This is for the "ebox cooling fan" - You can ignore it for E28 installations.
NC,
BR/GN (To BR/GN Oil Press Switch)
GN/WH (Connected to pin 6 on 20X connector)
BR (Ground)

You can just ignore this connector

Black 8 pin - Not needed, but has some useful stuff on it
Yellow - to TPS
Red - ECU Pin 36 - 12V Main Relay Output
Red/Blue - Switched 12V from Main Relay 87a
Brown/White - ECU Pin 51 - Auto kickdown switch input
Black - to TPS
Brown - to TPS
Brown/Green - ECU Pin 3 - Fuel Pump Relay Control


Black 2 pin - ??? Probably not needed - I think this connects to the AC switch on an E34/E32???

[demetk]

CEK, I don't think you need any of those harness connectors for your install. Let me take a look at what I've done under the dash and post a pic, but I'm pretty sure I just took two wires from c103 and spliced them to the appropriate pins on the ecu connector as was described in the faq.

What year/model e34 harness do you have?

[tig]

What year/model e34 harness do you have?

I'm not sure. Seller told me it was from an E34.

Appreciate you taking a look! I'm sure I could just ignore all that stuff and splice in the C103 wires for 40 & 41, but I HATE not understanding the details.

[tig]

FWIW, this link has been super useful to me in ensuring I'm doing things right...

http://www.e30zone.net/e30zonewiki/inde ... tronic_1.3

[demetk]

What year/model e34 harness do you have?

I'm not sure. Seller told me it was from an E34.

Appreciate you taking a look! I'm sure I could just ignore all that stuff and splice in the C103 wires for 40 & 41, but I HATE not understanding the details.

So I did not use those connectors on the e28. In fact, for my M1.3 install, I completely cut them off and taped the wires into the harness for a cleaner look.

Here's some pics of where they connect to my 89 e34.





On the e28, these are the only two c103 connections I did directly to the ecu harness as described in this faq.



Main relays and fused main power feed wire I mounted here.

[tig]

Demetk = hero.

[tig]

Buttoning up the harness and a few things have me stumped.

First is the green wire that comes off #86 on the main relay. It's not going anywhere now.

I think it's supposed to go to the C103:


Here's what it looks like inside the car:


The C103 pins
1 - Black - Goes to Tach. Comes from Pin 6 on ECU (B35).
2 - Green - Goes to OBC Relay Box (pin 4). Comes from ???.
3 - White - Goes to economy meter. Comes from pin 32 on ECU (B35).
4 - Green/Yellow - Goes to AC Switch (sort of). Not connected on B34. Comes from Pin 40/41 on ECU on B35.

On my B34 pulled out of Vlad it does.

However, in all the instructions above regarding C103 people say "Just hook up pins 1 & 3".

This doesn't seem right. Can someone confirm that this is supposed to be hooked up for a B35.

[tig]

While you guys are helping with the C103 above, let's talk O2 Sensors and O2 Sensor Relays.

The outputs from my O2 Sensor Heater Relay, seen here just off the eraser of the pencil aren't connected anywhere yet.


The Green/Brown wire coming of of #85 of the O2 Sensor Heater Relay is not connected to anything.

According to the E28 ETM, these relay connections are:
30 - Green/Blue - Goes to O2 Sensor Heater (white)
85 - Green/Brown - Goes to ECU Pin 31 (O2 Sensor Heater Control)

On the E34/B35:
ECU Pin 10 is O2 Sensor Ground
ECU Pin 23 is O2 Sensor Heater Control
ECU Pin 28 is O2 Sensor Input

The O2 Sensor Connector (on the engine) has the following leads:
1 - Yellow - Sensor Ground - To ECU Pin 10
2 - White - Sensor Input - To ECU Pin 28
3 - Ground
4 - Green/Violet - Heat - (From 87 on Relay)

This is all fine and dandy, however, my ECU connector has NO CONNECTION at Pin 23. I have two B35 harnesses. There is no connector on Pin 23 of either of them!??



Where do I wire the input (#85) of the O2 Heater Control Relay from?!?

[demetk]

Are you sure that is pin 23?

[tig]

Are you sure that is pin 23?

Pretty sure.


http://www.e30zone.net/e30zonewiki/inde ... tronic_1.3

[demetk]

Are you sure that is pin 23?

Pretty sure.


http://www.e30zone.net/e30zonewiki/inde ... tronic_1.3

Is that pin numbering for the wiring face or the mating face?

[tig]

Are you sure that is pin 23?

Pretty sure.


http://www.e30zone.net/e30zonewiki/inde ... tronic_1.3

Is that pin numbering for the wiring face or the mating face?

Mating face. Although it wouldn't make any difference. Pin 1 is farthest away from wire bundle and on the longer row. Can't screw that up.

[demetk]

So that looks be a mistake in the ETM. Mine doesn't have a pin at 23 either but my o2 sensor relay works. How many brown/green wires at the harness ecu connector? I wonder if they spliced 3 & 23 together and didn't update the schematic. I'll bet there's only one trigger for both the o2 relay and the fuel pump relay and it happens at pin 3.

[tig]

So that looks be a mistake in the ETM. Mine doesn't have a pin at 23 either but my o2 sensor relay works. How many brown/green wires at the harness ecu connector? I wonder if they spliced 3 & 23 together and didn't update the schematic. I'll bet there's only one trigger for both the o2 relay and the fuel pump relay and it happens at pin 3.

I just downloaded the 1991, 1992, and 1993 E34 ETMs just to see if an updated ETM (over 1990) would be different.

All of these ETMs include a nice ECU pin-out that show Pin 23 as "Not Used".

In addition in 1991-93 the O2 Sensor Heater is fed by #87 on the Fuel Pump Relay. Interestingly, the Fuel Pump Relay input is hot always/not fused. This means that on E34s the O2 Sensor Heater is not fused either! Odd, but BMW knows best.

So, there you go. Not only is the 1990 ETM wrong, but the ECU documentation on E30 Zone is wrong. And Demet is right.

It turns out I had mistakenly connected the output (87 Green/Violet) of the fuel pump relay to the line that feeds the o2 sensor heater in the o2 sensor connector. This would have worked fine, and I could have removed the Heater Relay, but not having it fused was bugging me. I also didn't like the fact that I had done this by accident.

Now pin 3 of the ECU now will close both the Fuel Pump and O2 Heater Relay.



The net of this is the E28 O2 Heater Relay is completely superfluous when moving to a B35! Pin 6 of C101 does not actually need to be connected to anything (other than the diagnostics connector, if you really care). Or you can do it the way I did.

[danc]

I'm really struggling to figure out how to wire in my harness. My problem is that I am un-willing to just blindly splice things together when either the colors or pin #s in the previous posts are ambiguous. I need to understand what goes where.



Black 8 pin - Not needed, but has some useful stuff on it
Yellow - to TPS
Red - ECU Pin 36 - 12V Main Relay Output
Red/Blue - Switched 12V from Main Relay 87a
Brown/White - ECU Pin 51 - Auto kickdown switch input
Black - to TPS
Brown - to TPS
Brown/Green - ECU Pin 3 - Fuel Pump Relay Control


Black 2 pin - ??? Probably not needed - I think this connects to the AC switch on an E34/E32???

You may have just answered the question (the one that no one is really asking) regarding how to incorporate an auto trans into the conversion.
I'm going to have to take a look at both ETMs (E28 & E34) and see if I can make sense of those TPS connections.

[tig]

A note on dipsticks:

I was using a red one in my M30B35. The handle broke today which made me check the 2 others I have; that's when I noticed they were different and I dug in to find out what was right. I didn't realize they were different lengths.

According to RealOEM the E28/M30B34 dipstick tube and the 89/E32/M30B35 tube are both 300mm.

The M30B34 dipstick is part #11431266740 and according to RealOEM should be 552mm.

The M30B35 dipstick is is part #11431718861. RealOEM does not specify a length, but does show it with a metal loop handle.

I measured the dipsticks I have and...

The two red dipsticks below have an overall length of 545mm. The metal part is 450mm. (They look different because of the camera angle; they are the same length).

The yellow dispstick has an overall length of 550mm. The metal part is 400mm.



The B35 oil pan is shallower than the B34 pan. Both blocks have the same length tube (300mm). I verified this by measuring the tubes on my B35 block and 2 B34 blocks. They are the same length; about 260mm meaning about 40mm is inserted into the block.

If you use a B35 oil pan you should be using part #11431718861.

[tig]

Why would I want a “B35” in my car?

Additionally, fuel economy should improve as well.

I averaged 36.7 mpg from Portland to Seattle yesterday. According to my OBC. My econometer seemed generous too; always wanting to be further to the left than I would expect.

IOW, something ain't right.

I've searched and found no one else complaining of their econometer/OBC read wrong after a swap. Maybe I just did a REALLY good job on this engine build? Haha.

Could be:

- I missed something in the swap instructions?
- I'm using 24lbs injectors and that's confusing it?
- Something else?

I sure would like my OBC/ecometer to be at least somewhat accurate. Whelp.

[Kyle in NO]

It's the 24lb injectors.